1
Background

1.1 Some History

As a child you probably played the swimming pool game of tag where you close your eyes and then repeatedly call out "Marco" with the response "Polo" each time from the other players by which you're supposed to locate them and tag someone who is then it. Biurnal hearing allowed you to tell which direction to lunge, and you could guesstimate who was nearby and who was farther away. The game is a little trickier to play at indoor pools because the acoustic scattering from walls and such can be confounding.

Marco Polo may or may not have traveled from Venice to China, although he did spend a couple of decades travelling and trading along the Silk Road, where he would certainly have picked up a lot of information, such as how to make power smoothies, and trade goods like yak hair [1]. He mistook rhinos for chubby unicorns, which is now a meme. In his book, he also claimed to have been besties with the emperor Kublai Khan. Christopher Columbus brought a copy of that book along with him on his 1492 trip to the Orient, but it turned out to be unhelpful. Navigating the world based on maps pieced together from stories of other travelers is always going to be a bit iffy. Fortunately, over the last century or so there has been a rapid development of navigation technologies.

The Submarine Signal Company, established in 1901 in Boston, was the first commercial enterprise organized to conduct underwater sound research and to develop equipment to be used for increasing the safety of navigation [2]. "Our invention relates to a method of ringing or sounding a bell and also to a system and apparatus for transmitting intelligence between ships at sea and between the shore and any ship by means of sound-signals made in the water at the transmitting-station by electrical means. These sounds are picked up from the water at the receiving-station by means of electrical or mechanical devices." The initial product line included underwater bells for shore-based stations, buoys, and lightships as well as encased microphones for sound detection on the ships [3, 4].

1.1.1 The Titanic Disaster

In 1912, the unsinkable Titanic struck an iceberg and sank [5]. Not long after, Sir Hiram Maxim self-published a short book and submitted a letter to Scientific American [6] in which he asked, "Has Science reached the end of its tether? Is there no possible means of avoiding such a deplorable loss of life and property? Thousands of ships have been lost by running ashore in a fog, hundreds by collisions with other ships or with icebergs, nearly all resulting in great loss of life and property." Maxim noted that collisions often take place in a fog at night when a searchlight is worse than useless because it just illuminates the haze. It was (becoming) known that bats used some form of sound that was outside the range of human hearing in order to echolocate and feed, but he thought it was infrasound rather than ultrasound [7, 8]. Maxim described a concept for a very low-frequency directional steam whistle or siren that could be used to (echo)locate icebergs during foggy nights when collisions were most likely to occur. Whether Maxim's patented apparatus would have been effective at preventing collisions at sea is a question that's a little like whether Da Vinci's contraptions would have flown. He got the general idea right, and can be credited with stimulating the imaginations of those who subsequently worked out all the engineering details.

His sketch, reproduced as Figure 1.1, is quite remarkable. The key idea is that the time delay of the echoes determines distance because the speed of sound is known, but more importantly, the shape of the echoes gives information about the object that is returning those echoes. Analysis of those echo waveforms can, in principle, tell the difference between a ship and an iceberg, and even differentiate large and small icebergs. He even illustrates how clutter affects the echoes differently from backscattering targets. Science has not, in fact, reached the end of its tether, even after a century of further development. This is exactly how radar, sonar, and ultrasound work [9, 10].

Maxim's suggested apparatus embodies a modified form of "siren," through which high-pressure steam can be made to flow in order to produce sound-waves with about 14-15 vibrations per second, and consequently not coming within the range of the human ear. These waves, it is asserted, would be capable of traveling great distances, and if they struck against a body ahead of the ship, they would be reflected toward their source, "echo waves" being formed [11]. This self-published pamphlet was discussed in [12].

1.1.2 Das Unterseeboot

The first submarine to successfully dive, cruise below the water surface, and emerge to the surface again on its own was the Sub Marine Explorer of the German American engineer Julius H. Kroehl, which already comprised many technologies that are still essential to modern submarines [13]. The first submarine built in Germany, the three-man Brandtaucher, sank to the bottom of Kiel harbor on 1 February 1851 during a test dive [14]. The Confederate States of America fielded several human-powered submarines, including CSS H. L. Hunley. The first Confederate submarine was the 30-foot-long Pioneer, which sank a target schooner using a towed mine during tests on Lake Pontchartrain, but it was not used in combat. It was scuttled after New Orleans was captured and in 1868 was sold for scrap, but the similar Bayou St. John submarine is preserved in the Louisiana State Museum. CSS Hunley was intended for attacking Union ships that were blockading Confederate seaports. The submarine had a long pole with an explosive charge in the bow called a spar torpedo. The sub had to approach an enemy vessel, attach the explosive, move away, and then detonate it. It was extremely hazardous to operate, and had no air supply other than what was contained inside the main compartment. On two occasions, the sub sank; on the first occasion, half the crew died, and on the second, the entire eight-man crew (including Hunley himself) drowned. On 17 February 1864, CSS Hunley sank USS Housatonic off the Charleston Harbor, the first time a submarine successfully sank another ship, although it sank in the same engagement shortly after signaling its success. Submarines did not have a major impact on the outcome of the American War Between the States,1 but did portend their coming importance to naval warfare and increased interest in their use in naval warfare.2

Figure 1.1 The infrasonic echo waves would be recorded by a stretched membrane that the infrasound waves would vibrate, and those membrane vibrations could jingle attached bells or wiggle pens tracing lines on paper as Maxim illustrated. Maxim's concept was discussed in Nature, a leading scientific journal yet today.

You almost certainly know Captain Nemo's submarine Nautilus from Jules Verne's Twenty Thousand Leagues Under the Sea (1870), but you may not have read The Mysterious Island (1874) or know that Nemo's fictional craft was named after Robert Fulton's real-life submarine Nautilus (1800). Verne was inspired by the French Navy submarine Plongeur, a model of which he saw at the 1867 Exposition Universelle. The fictional Nautilus was battery powered, not nuclear like today's boomers that can travel way more than 20,000 leagues (not quite three laps around the earth) under the sea, sneaking around for six months at a time just in case they need to destroy the world because reasons.

The Battle of Hampton Roads was the most important naval battle of the American Civil War. It was fought over two days in March 1862, where the Elizabeth and Nansemond rivers meet the James River just before it enters the Chesapeake Bay adjacent to the city of Norfolk, Virginia. The battle was a part of the effort of the Confederacy to break the Union blockade, which had cut off Virginia's largest cities and major industrial centers, Norfolk and Richmond, from international trade. The battle was the first meeting in combat of ironclad warships: USS Monitor and CSS Virginia. USS Monitor was a semisubmersed, iron-hulled steamship and was the first ironclad warship commissioned by the Union Navy. Her remains were found upside down 16 miles off Cape Hatteras in 1973 at a depth of about 240 ft. In 1987, the site was declared a National Marine Sanctuary, the first shipwreck to receive this distinction. Because of Monitor's advanced state of deterioration, recovery of any remaining significant artifacts and ship components was quite urgent. Numerous fragile artifacts, including the innovative turret and its two Dahlgren guns, an anchor, steam engine, and propeller, were recovered. They were transported to the Mariners' Museum in Newport News, where a full-scale copy of USS Monitor, the original recovered turret, and a variety of artifacts and related items are on display.3 Also in Newport News is the largest military shipbuilder in the United States and sole designer, builder, and refueler of nuclear-powered aircraft carriers. HII is responsible for building more current aircraft carriers than the rest of the world's navies put together. Virginia would be a superpower if they seceded today.

Most consider French physicist Pierre Curie's discovery of piezoelectricity in 1877 to be the moment...